The present invention relates to lavatory cleansing blocks, their use and a method for their preparation.
Solid lavatory cleansing blocks are well known in the art. Such blocks are typically designed to release active materials, including fragrance (or perfume), throughout their life. For example ITB (in the bowl) lavatory cleansing blocks are known which are hung from the rim of the lavatory bowl in a conventional container and which are designed to release fragrance and cleansing components upon dissolution of the block when the toilet is flushed. Additionally ITC (in the cistern) lavatory blocks are known for cleansing toilet systems; such block is placed in the cistern so that when the toilet is flushed cleansing components are released with the flush water into the toilet bowl.
Such lavatory cleansing blocks are conventionally based on a single homogenous formulation, which typically comprises a mixture of one or more bleaching agents, surfactants, fragrances and binders.
A disadvantage with such blocks is that a constant release of active materials throughout the life of the block cannot be achieved. The rate of release of an active material is linked not only to the concentration of the active material in the block but also to the size of the block. Thus a reduction in the surface area of the block during the life thereof will result in a reduction in the level of release of the active material.
WO 96/14392 (Henkel KG) discloses a cleanser in bar form for flush toilets, consisting of at least two different aggregates placed together, whereby one of the aggregates is at least partially enclosed by the other aggregate or aggregates, wherein the enclosed aggregate and at least one of the other aggregates contain at least a same active ingredient, whereby the concentration of at least one of these active ingredients in the enclosed aggregate is at least 1.3 times the concentration of the same active ingredient in the enclosing aggregate or aggregates.
The above active ingredient may be, for example, a perfume. Water penetrates into a lavatory block during use of the block. Towards the end of its life, a block may contain a significant proportion of water. Thus, in the case of the above block, the fragrance, which is the same in both regions of the block, will nevertheless not perform in the same way throughout the entire life of the block as the block absorbs more and more water. Furthermore it is known that the amount of fragrance contained in a formulations is key to determining the final rheology of the paste. If the same fragrance is present in two formulations in different amounts as in the above block, the rheologies may be vastly different such that co-extrusion of the two regions would be very difficult without readjusting the rheology of the two pastes.
We have now devised a block comprising at least two regions which is suitable for use as a lavatory cleanser and which allows active ingredients to be released from the block at a relatively constant rate over time in which the concentration of the fragrance in the inner region is not significantly greater than the concentration of the fragrance in the outer region. Since different fragrances are used in the inner and outer regions it is possible to use fragrances which take into account the problem of water penetration into the block. A fragrance can be used in the inner region which is more easily delivered from a wet block. Furthermore the rheologies of the inner and outer phases can be more easily controlled.
The present invention provides a lavatory cleansing block having a perceived approximately constant intensity of fragrance throughout the life of the block, which comprises an inner region comprising an inner fragrance and an outer region comprising an outer fragrance which is different from said inner fragrance, the inner fragrance being present in a concentration by weight which is less than or equal to 1.1 times the concentration of the outer fragrance.
The present invention also provides the use of a block as defined above as a lavatory cleansing block.
The present invention additionally provides a method of preparing a block as defined above which comprises extruding the inner region and outer region to form a solid block.